1. Field of the Invention
The present invention relates to a recording tape cartridge which rotatably accommodates a reel around which a recording tape, such as a magnetic tape or the like, is wound.
2. Description of the Related Art
Recording tapes such as magnetic tapes and the like are used as external recording media for computers and the like. Little space is required to accommodate such a recording tape at the time of storage thereof, and a large amount of information can be recorded thereon. A so-called single-reel recording tape cartridge is used in which a single reel, on which the recording tape is wound, is rotatably accommodated within a case.
Such a recording tape cartridge has a braking means so that the reel does not rotate within the case when the recording tape cartridge is not in use (see, for example, U.S. Pat. No. 5,813,622). This U.S. Pat. No. 5,813,622 discloses the following structure: an engaging gear is provided in an annular form at the floor surface of a reel hub which is shaped as a hollow cylinder having a floor and which structures the axially central portion of a reel. A braking member, which is disc-shaped and at which is provided a braking gear which can mesh with the engaging gear, is inserted within the reel hub. The braking member is supported so as to be unable to rotate with respect to the case, and so as to be slidable in the axial direction of the reel. Due to the urging force of a compression coil spring provided between the case and the braking member, the braking gear is made to mesh with the engaging gear of the reel. In this state, the reel is pressed against the floor plate of the case by the urging force of the compression coil spring. Rotation of the reel with respect to the case is locked due to the braking gear of the braking member meshing with the engaging gear due to this urging force.
In this structure, a pass-through hole is formed in the floor portion of the reel hub. When a releasing portion of a drive device enters in from this through hole and pushes the braking member upward against the urging force of the compression coil spring, the meshed-together state of the braking gear and the engaging gear is cancelled, and rotation of the reel with respect to the case is permitted. The releasing portion of the drive device is provided at a rotating shaft together with a driving gear which meshes with a reel gear formed at the end surface of the reel hub. As the driving gear meshes with the reel gear, the releasing portion pushes the braking member upward. Accordingly, in this structure, when the rotating shaft drives and rotates the reel, the braking member, which cannot rotate with respect to the case, and the releasing portion, which rotates integrally with the rotating shaft, slidingly-contact one another while being pressed against one another due to the urging force of the compression coil spring. In order to reduce the resistance to rotation which arises accompanying this sliding-contact, the braking member and the releasing portion are both formed of resin materials.
Further, a structure which is similar to that disclosed in above-described U.S. Pat. No. 5,813,622 has been conceived of in which a releasing member, which rotates integrally with the reel, is provided between the braking member and the floor surface of the reel hub (see, for example, U.S. Pat. No. 5,901,916). Specifically, due to the releasing member being pushed by a releasing portion of a drive device, the releasing member is pushed upward together with the braking member against the urging force of the compression coil spring. In this way, the braking member is pushed upward by the releasing portion via the releasing member, and the locked state of the reel is cancelled. In this structure, due to the releasing member rotating integrally with the reel at the time when the reel is driven to rotate, the releasing portion and the releasing member do not slidingly-contact one another, and the releasing member and the braking member slidingly-contact one another.
Moreover, a structure is known in which, at the time when the reel is driven to rotate, the braking member does not slidingly-contact any other portion (see, for example, U.S. Pat. No. 6,271,991). In this structure, the engaging gear is formed at the outer peripheral portion of a flange of the reel. Rotation of the reel is locked due to two braking members, each of which is swingably supported within the case and is urged in a direction of meshing with the engaging gear, meshing together with the engaging gear. Further, when this recording tape cartridge is loaded into a drive device, the locking members are pushed by releasing portions of the drive device, and swing against the aforementioned urging force. In this way, the meshing together of the locking members and the engaging gear is released, and rotation of the reel is permitted. These releasing portions are respectively provided independently of the rotating shaft, and push the locking members due to the loading of the recording tape cartridge (the case) into the drive device or the lowering of the recording tape cartridge (the case) within the drive device. In this structure, the compression coil spring, which is for pressing the reel against the case or the rotating shaft, is connected to the reel via a bearing. Relative rotation between the compression coil spring and the reel is absorbed by the bearing.
However, in the recording tape cartridges relating to the above-described structures, when the recording tape is not being used, the reel is pressed against the floor plate of the case by the urging force of a compression coil spring. Therefore, when force resisting the urging force of the compression coil spring is applied, upward and downward movement of the reel within the case cannot be impeded (locked). Thus, for example, if the region where the reel gear is formed at the reel, which region is exposed from the case (i.e., the outer surface of the floor portion of the reel hub), were to be pushed or if impact of a drop were to be applied to this region, the reel would joggle greatly within the case, which could be a cause of damage to the recording tape whose one end portion is held at the case via a leader member.
Moreover, in the structures disclosed in U.S. Pat. No. 5,813,622 and U.S. Pat. No. 5,901,916, the urging force of the compression coil spring is applied as drag to the region of sliding contact between the braking member and the releasing member, or between the braking member and the releasing portion of the drive device. Therefore, when, in accordance with the trend of making recording tape cartridges have higher recording capacities, the recording tape is made to be longer and the rotational speed of the reel is made to be a high speed, or the time over which the reel is continuously driven is extended, there is the concern that wear will arise at these regions of sliding contact. On the other hand, in the structure disclosed in U.S. Pat. No. 6,271,991, the urging means for urging the braking members in the direction of meshing with the engaging gear, and the compression coil spring which urges the reel toward the floor plate of the case, are separate members. Therefore, the relative rotation between the reel and the compression coil spring cannot be absorbed by the braking members which rotate relative to the reel, and this relative rotation must be absorbed by an expensive bearing.
In this way, in conventional recording tape cartridges, there is still room for improvement of the structure for holding a reel in a case when the recording tape cartridge is not being used.